Method of determining stream line contours



Patented Jan. 5, 19 32 barren STATES PATENT OFFICE.

CHARLES r. 'IOLMAN, OF NEW YORK, N. 2.,nss1enon OFVJONE-HALF, TO PETER o;

MCNULTY, OFYMILWAUKEE'WISCONSIN METHOD or DETERMINING sain'nAisrLinn coN'roUns No Drawing.

The invention relates to a method for accurately determining the proper stream line contours for aeroplanes and their appurtenances, such as wings, rudder, running gear, ailerons, narcelles, etc.

Heretofore it has been the practice to arrive at the contour of aeroplanes, their wings and other parts which are exposed to the elements by a method of successive appropriations whereby starting with an assumed design or with a design embodying certain assumptions improvement has gradually been developed by comparative tests and by mathematics based upon data obtained from such designs, such former methods being in effect a cut any try process. The object of the present invention is to quickly and readily design parts of an aeroplane subjected to stream line flow which accurately conform to the natural laws of stream line flow past these.

parts so that following the present method the parts of the aeroplane may be readily designed to have the proper stream line contour.

The invention furtherconsists in the method or steps of the method hereinafter described and more particularly defined by claims at the conclusion hereof.

The process, in brief, consists in subjecting an aeroplane, either of full size or of model size, to the action of flow or air in asuitable wind tunnel and causing a deposition of some suitable substance upon the partgoing under testso that the final contour of the surface past which the air is flowing will be built up,

to the proper contour to conform to actual conditions when the aeroplane issubj ected to Application 'filed' November is, 1929. Serial- No. 408,175.

the aeroplane or its counter model to afflow of air at suitable velocity and injecting into the air a spray of water, or steam which is carried into the stream of freezing air and brought into impinging contact with the plane in order to freeze thereon, particularly inthe deadcorners and other regions where there is an. eddying efiectit being particularly note d that the greater deposition of fr ozenparticles will occur at the dead corners and in the regions where there is an eddying eii'cctso that these deficiencies of thedesign may becorrected.

i 7 By this action the shape will be gradually built; up, always approaching true stream line contours. Vi hen the point has been reached which on observation shows no substantial change in contour, the change being onlyla, general building up over the whole area, the air'blast and water spray is shutoff and the contour of the surface is ready for recording by direct measurement. 7 This point might be determined, when'the work is being done in a regular wind tunnel, by noting the load on the means by which the head resistance of theaeroplane is'measured. Vhen this resistance has reached a minimum and begins to'show an increase the process should be stopped. Measurements can be made in any well known manner, as, for example, by measurementsreferred to known coordinates 'bybe nding thin stripsof plastic material, such as lead, about the surfaces and-subsequently scribing the curves so reproduced;

means of inoldsmade of plaster of Paris or other suitable material; or by such other method or methods as may prove most convenient or suitable to obtain the measurements of-the contour produced in accordance with this method. 7

, It is desirable to produce. in the wind tunnel those atmosphericconditions under which sleet forms on an aeroplane in actual service.

'One specific manner of carrying out the invention has beendescribed above for the sake of simplicity, but there are obviously many alternatives, as, for example, instead of using freezing atmosphere and water in this'process, air at ordinary'temperatures or v:

hot airl'could be used and any combination fl t) It is also clearly obvious that the areos plane could be sprayed fr'om'time to time with adhesive material, such as glue, and subsequently blasted with air carrying finely divided solids to produce the sameresult.

Obviously the general type of aeroplane should i be embodied. in the model I is subjected'to the process,but in some instances lowing the same to congeal thereon until no further improvement in the shape of the surface takes place, as indicated by a measured increase in resistance of the surface to the flow of the air stream. 7

In testimony whereof, I aflix my signature.

CHARLES 1P. TOLMAN.

it might be desirable to skeletonizelall'o'r j certain parts of the structure.

While the invention has been described is of extreme importance with reference with particular reference to ai'eoplane sjantl thereto, it is within tlie scope'of 'the same I to utilize the process hereinbefore described in connection w th high speed transportation vehicles'of 'known'forms and types 'COIlIlCtlOn with the determining of the proper stream line contour of other surfaces subjected to a flow-of air or other fluids so that in its broad aspect the invention is not with aeroplanes. 1 r

I desire'it to' be understood that this invention is not to be limited to any particular material for carrying the process into effect except'insofar'as such limitations are contained in the claims. i

YVhat I claim as my invention is:

l. The method of determining the stream line contour of'aeroplane surfaces or of the parts or auxiliaries'thereof which are subjected to air fiowfivhich consists in subjecting the aeroplane or said surfacesto a flow of air past the surfaces, intr oducingfa substance into said flow of air for deposition on V to be limited solely to its use in connection said surfaces in accordance with the natural laws governing streamline flow over 'said surfaces brlnglng about a condit on producing a deposition of said substance on said surfaces, and continuing said deposition until. the optimumshape is obtained'as in dicated by air resistance measurements made s multaneously wlth the subjection of sa d surfaceto the air flow and deposition.

this wind tunnel at freezing temperature,

spraying a fluid capable of freezing into said air and depositing the sprayed; fluid upon the surfaces be ng treated m accordance with the naturalflow of airpast said surfaces and al- N 

